I am 19 years old boy i am so thin i eat more bt i could nt gain waight.plz help me.should i take any medicine?

See below: See doctor to be checked for overactive thyroid, diabetes, intestinal parasites (tapeworm etc), malabsorption syndrome. May be that u are very active & burn off the calories u eat. Eat protein, good fats, low glycemic carbohydrates.

If healthy, protein: If you are feeling well, and ideally have been evaluated by a physician recently to be sure you do not have a metabolic condition (such as thyroid disease or diabetes) and are not taking stimulant medications, then adding a protein supplement to your regular diet--without reducing your usual intake--can help. This can be as a snack bar, meal-replacement bar, or powder you add to drinks.